Description standby tt 48 12 channels. Automatic telephone exchange

The software for the administration system of the PTK VECTOR-VT is a Web application that runs in any Internet browser (Internet Explorer, Opera, Mozilla Firefox). Thus, to monitor and manage the device, there is no need to install any specialized software on the administrator's computer.

The administration system allows you to perform the following tasks:

• telegraph channels configuration;
• configuring PM channels;
• configuring the PM channel with the multiplexing of telegraph channels and telephone channel; adding, deleting and configuring virtual IP channels;
• configuration of code-independent channels of IP-special consumers;
• carrying out measurements on telegraph channels;
• monitoring the status of any type of channels;
• adding, deleting and modifying alarm profiles;
• backup archiving and fast restoration of PTK VECTOR-VT settings.

Configuring telegraph channels

The administration system allows you to perform all the basic actions necessary to set up telegraph channels:

• setting the data transfer rate over the channel, corresponding to the speed of the connected subscriber (selection from the list 50, 100, 200 Baud);
• selection of alarm type from the list of profiles. From the list, you can select both a code-dependent signaling profile and a code-independent operation mode of the special consumer channel;
• turning off the channel in case it is not used;
• setting up routes for organizing connections to a TT circuit or virtual IP circuit.

Configuring PM Channels

The main actions when working with PM channels:

• selection of the type of equipment from the list of preset configurations of PM channels for the corresponding types of equipment (TT-5, TT-12, TT-24, TT-48, TT-144, P-327, P-318, P-314, etc.);
• manual setting of the distribution of TT channels in the PM channel for mixed-type systems or for those that are not in the list of preset configurations;
• setting the levels of input and output signals, as well as enabling or disabling the transmission of the control frequency;
• configuring the PM channel using the spectrum of the PM channel for multiplexing telegraph channels and a telephone channel is reduced to selecting the appropriate type of equipment and setting the telephone filter mode. As a result, one of the PM channels will be used as a compressed telegraph and telephone, and the second will be used to connect a telephone line.

Configuration capabilities allow the channel to be configured to work with any type of frequency division CT equipment at an adjacent node.

Configuring IP Channels

For IP channels, operations are available for creating an almost unlimited number of virtual telegraph channels and various manipulations with them. The speed of the IP channel is determined automatically, which eliminates the need to manually set the data transfer rate over the channel. Configuration comes down to prescribing routes for organizing connections with physical telegraph lines and TT channels.

Virtual telegraph channels support data transmission in a code-independent traffic mode for special consumers over an IP network. This mode is activated automatically when a connection is established with a code-independent telegraph channel serving a special consumer. Thus, no additional steps are required to connect the special consumer to the IP network.

Carrying out measurements of telegraph channels

The administration system allows measurements to be made on physical telegraph and TT channels. All actions are available both for a separately selected channel and for an arbitrarily selected group of channels.

If necessary, it is possible to make a turn in the direction of adjacent equipment via the telegraph channel.

A signal of positive and negative polarity can be output to the telegraph channel, and the channel output can also be turned off.

In the direction of adjacent equipment, it is possible to transmit “point” test signals via a telegraph channel with a choice of speeds of 50, 100, 200 Baud.

If it is necessary to estimate the percentage of edge distortions in the channel, the PTK VECTOR-VT has a mode for measuring test signals "points". This displays the speed of the measured signals and the percentage of edge distortion separately for positive and negative polarity.

Channel monitoring

The administration system allows you to remotely view the status of channels in the pool of telegraph channels, PM channels and IP pools.

The displayed information shows the real state of the working channel - the channel can be in the initial state, in operation, in test mode, and also in an emergency state. In the latter case, the cause of the crash and its duration is displayed in the administration system. This may be a break in the receiver line, a short circuit in the transmitter, polarity reversal, etc. Each channel state has a corresponding color indication.

The emergency states of the channels are accompanied, among other things, by an audible alarm on the administrator's computer.

Alarm profile management

The profile settings dialog is designed to manage alarms. Operations are available for creating new signaling profiles, deleting unused ones, as well as fine-tuning existing profiles.

In most cases, pre-installed profiles with ready-made alarm settings are sufficient, but if necessary, fine adjustment allows you to connect any subscriber device with a non-standard communication protocol to the VECTOR-VT PHC.

Backup archiving and quick restoration of settings

The administration system allows you to manage the general settings of the complex and back up the entire configuration of the PTK VECTOR-VT.

Saving and restoring the complete configuration of the complex is carried out by the command of the administrator "with one click of the mouse". The simplicity of this operation allows you to always have a backup copy of the configuration on a personal computer and, if necessary, in a matter of seconds, remotely restore the functionality of the PTK VECTOR-VT.

If a large number of devices are used in the IP network, all VECTOR-VT hardware and software complexes can be backed up from one personal computer connected to the IP network. At the same time, the principle of centralized management, redundancy and control of all devices in a distributed IP network is achieved. It is clear that being, for example, in St. Petersburg, you can safely administer the VECTOR-VT hardware and software complex installed in Khabarovsk or Murmansk, if, of course, you have the appropriate access rights and are in the same IP network with them.

Alarm system

The alarm system is integrated into the administration system and is designed to notify the operational and technical personnel about hardware and software failures of the PTK VECTOR-VT, as well as about emergency situations that occur on communication lines and channels.

Failure alarm is accompanied by audible and visual indication. At the same time, there is no need to install special software, the alarm system is automatically activated when connected to the VECTOR-VT control panel from a web browser from any personal computer.

Channel-forming telegraph equipment

Topic 5.1 Construction of equipment for the formation of telecommunication channels

General information about channel-forming equipment

Channel-forming equipment - technical means that allow the use of a standard PM channel for organizing several telegraph communications. Telegraphy in this case is called tonal. On the receiving side, one message is separated from another either due to the fact that the messages occupy different settings in the frequency band 0.3 - 3.4 kHz - FDM, or because they arrive at different times - TDM.

Equipment with PMC type TT-12, T-48, TT-144, equipment with VRK type TVU-12M, TVU-15, DATA, DUMKA.

In FDM equipment, the channels formed in the PM band are numbered. The number of each channel consists of 3 digits: the first indicates the type of channel (1-50 baud channels, 2-100 baud channels, 4-200 baud channels), 2 subsequent digits - the serial number of the channel from the lower limit of the frequency band 0.3 kHz to upper 3.4 kHz. So the channels tone telegraphy 50 baud are numbered 101-124 / 24 CT channels in a standard PM channel); with a speed of 100 baud are numbers 201-212; at 200 baud - 401-406.

The main elements in the equipment with TRC are the multiplexer and the UPS signal conversion device. The multiplexer combines the transmission of telegraph signals coming from different sources into a single digital stream, and distributes this stream to the corresponding receivers at the reception. The UPS coordinates the parameters of the digital stream with the parameters of the transmission channel.

Topic 5.2 Channel-forming equipment with frequency division of channels.

Technical data TT - 144

The TT-144 equipment is used to organize low-speed channels on the backbone sections of the telegraph network and data transmission network. The TT-144 voice-frequency telegraphy equipment allows organizing up to 144 two-way discrete channels in the frequency band of the PM channel of cable, air and radio relay communication lines. The equipment uses frequency division of channels and frequency modulation. In one TF channel, the equipment allows you to organize the following number of discrete channels: 24 with a speed of 50 Baud, or 12 with a speed of 100 Baud, or 6 with a speed of 200 Baud, or 1 with a speed of 1200 Baud and 6 with a speed of 50 Baud (or 2 with a speed of 200 Baud). Baud). The numbering of channels, carrier frequencies, the distance between them and the frequency deviation "in the linear spectrum of the PM channel comply with the requirements of GOST and the recommendations of the CCITT. The equipment also allows organizing mixed groups of channels of different speeds in the PM channel.

The equipment uses the principle of individual-group conversion. The group of channels occupying the frequency band of 3.6...5.01 kHz was taken as the initial one. Group carriers with frequencies of 5.4 and 6.84 kHz are used for conversion. Telegraph sets, equipment and subscriber sets for data transmission, switching telegraph stations operating with two-pole parcels with a voltage of ± (5 ... 25) V can be connected to the equipment. In TT channels, under normal operating conditions, edge distortion does not exceed 5%. The input and output resistances of the CT channels are 1000 ohms.

Structural diagram of TT-144 equipment

The block diagram of the TT-144 equipment contains the main blocks: RNG frequency grid generator blocks, interface C blocks, blocks linear equipment LO, K channel blocks, KP predominance compensator block, power supplies. In addition, there are a number of auxiliary blocks.

The frequency grid generator is designed to form the entire set of highly stable frequencies necessary for the operation of equipment nodes. It consists of a block of reference frequencies OC. group frequency block MS. blocks of linear frequencies of the LF, blocks of shapers F. The block SP contains a quartz oscillator and provides the formation of periodic pulse oscillations with a frequency of 3,932,160 Hz for the operation of the remaining RNG blocks. To form 21 linear frequencies, there are seven identical blocks LCH1-LCH7. To change the linear frequencies of the channels, the LF outputs are connected to the channel blocks through the switching board of the linear frequencies of the CL. The HF block is designed to generate oscillations of carrier frequencies (5.40 and 6.84 kHz) of group converters and a frequency of 2.7 kHz to control the CFP. Frequency modulators and demodulators of blocks K are provided with the necessary frequencies using two blocks F, containing five shapers each, performing the functions of power amplifiers.

The LO block is designed to match the PM channel with the individual equipment of the TT channels in terms of the frequency spectrum, levels and resistances, as well as to signal a low level in the PM channel. It consists of transmitting and receiving parts, each of which has two signal conversion paths, with a conversion frequency of 5.4 kHz (group A) and 6.84 Hz (group B). The block contains group converters of spectra P, amplifiers Us and low-pass filters of LPF. In group low-pass filters, transmissions are delayed from entering the HF channel by harmonic components from carrier frequencies and upper sidebands present at the outputs of the CFP. In the group LPF of the receiving part, the spectrum of the group signal is limited to eliminate the influence of the multiband CFP.

In the group amplifier of the receiving part of the LO block, a stepped AGC is used. When the level of the group signal is lowered by 9 dB, the gain of the group amplifier increases stepwise by 9 dB. Interface device C is individual equipment designed to convert signals coming from local telegraph circuits (in terms of voltage and current) into signals necessary for the operation of the K channel unit (on transmission) and inverse conversion (on reception). In one block C there are three junction devices, each of which consists of an input and output device. Interface devices are universal and are used for all information transfer rates provided in the equipment.

In the universal block K, DC telegraph messages are converted into frequency-modulated signals at transmission and frequency-modulated signals into telegraph messages at reception. The block consists of a transmitter and a receiver, and all its nodes are located on two boards: on one CFP trans and CFP pr, and on the other the rest of the devices. Block K with the help of resoldering can be transferred to one of three modes for operation at a nominal speed of 50, 100 and 200 Baud / Frequency modulators and frequency detectors of the block operate in all modes at an average frequency of 2.7 kHz.

The transmitter of the universal channel block consists of the following main components: an FM frequency modulator, an additional transmission filter (not shown in the figure) and a commutated transmission filter-converter KFP per. The FM inputs from the RNG receive pulse sequences that are multiples of the lower characteristic frequency and the difference between the characteristic frequencies. Depending on the polarity of the parcels coming from the junction device, the lower or upper characteristic frequency is generated at the FM output. In the absence of a telegraph signal at the input of the equipment, the lower characteristic frequency enters the FM output.

The additional transmitter filter is a low-pass filter and is designed to suppress odd harmonics of a rectangular signal coming from the FM output. CT from a center frequency of 2.7 kHz to a line frequency of 3.66-.-4.98 kHz, specific to each channel. To do this, a control signal fl With a frequency equal to the required line frequency of the channel in the group.

Picture. Structural diagram of TT-144

The receiver of the channel block consists of a CFP, etc., an additional filter for receiving DF, etc., a limiting amplifier (UO), and a frequency discriminator for the frequency response. LPF. threshold device PU, as well as the circuit of the level detector DU (DF pr. and DU are not shown in Fig. 8.34). From the group signal, the CFP pr. extracts the oscillations of a given TT channel and transfers the spectrum of the selected signal from the linear frequency to a frequency of 2.7 kHz. An additional receive filter delays the odd harmonics of the signal generated at the output of the CFP, etc. The limiting amplifier used in the equipment is described in detail in § 8.2.1. The frequency discriminator converts the FM - signal, and a series of pulses, the duration of which depends on the frequency of the input signal; the principle of its operation is similar to the operation of the BH equipment TT-12.

The low-pass filter extracts a constant component from the pulse sequence at the BH output, the value of which changes linearly with the frequency at the receiver input. The threshold device of the channel is intended for the formation of rectangular telegraph signals. The bipolar rectangular pulses generated by the PU control the operation of the output device of block C. When the signal level at the receiver input is below the minimum allowable value, the DU generates a blocking signal that sets the PU to a position that ensures the appearance of a start message in the local telegraph circuit. From the CP predominance compensator block, the CP also receives a predominance compensation signal generated by the CP during a frequency shift in the PM channel. The KP block contains a transmitter that generates an unmodulated signal with a frequency of 3.3 kHz, and a receiver similar to the TT channel receiver. except that after the black hole, the signal is not fed to the PU, but to the inverting amplifier. At the output of the receiver of this channel, a constant voltage is generated, the value of which is proportional to the frequency shift in the PM channel. This voltage is applied to the threshold devices of the CT receivers of all channels and changes their thresholds, thus eliminating dominance distortion.

The BK channel block for 1200 Baud, which is part of the TT-144 equipment and provides, using frequency modulation, the transmission of discrete signals at speeds up to 1200 Baud, differs from other K blocks in that it contains an individual crystal oscillator and non-CFPs are used as bandpass filters , and 2, C-filters. Compared to the TT-48 and TT-12 equipment, the TT-144 equipment has an expanded range of operational devices, which makes it possible to reduce the time spent on equipment maintenance. These devices include a sensor of test signals DS, a control unit for the tone frequency channel of the KFC, a BI indication unit with an intercom, and signaling units BS1 and BS2. The signaling block BS2 is included in each section of the TT-48, all other blocks are located in the row of control and signaling of the RCS. Test telegraph signals of the form 1: 1 are formed in the DC with speeds of 50, 100, 200 and 1200 baud, as well as the signals "Pressing +" and "Pressing -", Using the BI, they carry out operational control: currents and voltages in local circuits; levels at the linear inputs and outputs, as well as at the inputs of the UO; the presence of predominance (up to ±10%) at the channel outputs. The display unit also allows you to organize telephone conversations during measurements and the entry of equipment into communication. The KFC block is designed to control the signal-to-noise ratio decrease in the TF channel (with response limits of 18, 24 and 30 dB) and the control frequency shift that exceeds the set threshold value of 2, 4, 6, 8 or 10 Hz. Blocks BS1 and BS2 generate alarm and warning signals. The alarm is activated in case of malfunction of the RNG, power supplies, blown fuses, underestimation of the reception level of any TT channel by 18 dB or the reception level in the PM channel by more than 20 dB. The warning alarm is triggered when the overall reception level in the PM channel is underestimated by more than 9 dB, the set threshold for monitoring the signal-to-interference ratio or frequency drift in the telephone channel is exceeded.

Questions for self-control

1. List the technical characteristics of the TT-144.

2. Explain the composition and purpose of the channel transmitter.

3. Explain the composition and purpose of the channel receiver.

general characteristics

Telephone exchange - a set of technical means designed for switching communication channels of the telephone network. At the telephone exchange, certain telephone channels are connected - subscriber and connecting communication lines - for the duration of telephone conversations and their separation at the end of negotiations; for this purpose, the unification and distribution of telephone message flows in the directions of communication is carried out. A telephone exchange is a type of communication center. Usually the telephone exchange is placed in a special building.

According to the method of switching, the telephone exchange is divided into manual (RTS) and automatic (ATS). RTS is equipped with telephone switches; channel switching is performed by a telephone operator.

PBX - automatic telephone exchange - is a special device with which a call signal is automatically transmitted between two or more telephone sets, while maintaining the ability to ensure both the establishment of a connection between them and the break. PBX can work with external telephone networks, such as: GSM, IP networks, city network, and with internal, i.e. between themselves. The main task of the PBX is to provide communication between subscribers of the internal network with the "outside world".

PBXs, depending on the type of switching devices used, are:

Decade-stepping - built on electromechanical seekers, respectively, with machine and electromagnetic drives;

Coordinate, in which multiple coordinate connectors serve as switching devices;

Electronic, for example, with switching by means of semiconductor devices (such automatic telephone exchanges are under development);

Digital - stations whose operation is based on forwarding by means of digital signals;

The main functions of the PBX.

The telephone exchange has many useful features that will help make your workflow more efficient by providing high-quality multi-channel communication:

Using an internal line for negotiations without the participation of the city. that is, during a conversation between participants in the internal PBX network, the city incoming line remains free;

Possibility of simultaneous conversation of internal and city network subscribers - conference call;

Automatic search for a free line to make an external call;

Notification of the release of the city line;

Ability to use the auto redial mode and call forwarding;

Mode "director - secretary";

Establishment of telephones to which external calls will be received;

Ability to set a different call for all types of calls;

Possibility to set restrictions on long-distance calls and some city numbers;

Remote listening of premises;

Ability to connect an answering machine, fax, modem;

Management of work of automatic telephone exchange through the computer.

The possibilities of a modern PBX are almost limitless, it allows you to expand the number of incoming lines and internal subscribers. The expansion is available due to the modular principle of building PBX, i.e. All you need to do is add an expansion board. This possibility significantly reduces costs, because the purchase of a new PBX requires significant costs, including its installation.

Composition and principle of operation of ATS.

The ATS includes:

1) switching system and control devices;

2) input devices for connecting telephone lines to the switching system;

3) installation of electrical power;

4) auxiliary devices (ventilation, heating, etc.).

The switching system (CS) and control devices (CU) are usually located in the automatic room.

PBXs are located in rooms called cross-country. In the cross, consisting of a subscriber cross and a cross of connecting lines, the inputs are concentrated, as well as the means of electrical protection of station devices from the effects of the lines. In the glove box, trunk (subscriber) communication cables and high-capacity trunk cables are divided into cables of smaller capacity, convenient for inclusion in cross-connect devices.

cross equipment.

CROSS- To switching- R distributive O equipment FROM system FROM ties: It serves to switch from multi-pair trunk (from the city PBX) or multi-pair cables of subscriber sets to wires going to subscriber telephone sockets at user workplaces. Ross are switching distribution equipment of communication facilities. Unified crosses are available in floor and wall versions. The floor structure of the cross consists of unified elements (strafes and modules) and allows the formation of crosses with one-sided (wall) and two-sided placement of the linear and station sides. The number of strafes and modules is determined by the capacity of the cross. Cross-country capacity is determined in numbers. One number includes a line and station pair and is designed to connect one two-wire line. The increase in capacity is made by splicing sections of the cross.

The design of the wall cross is unified on the basis of the elements of the floor version. Cross-connect capacity, depending on the length of the mounting rails, ranges from 100 to 1000 subscriber and trunk lines with the possibility of expansion. The main elements of the cross are plinths and service accessories. Plinths are used to connect cables and crossover wires. Plinths are produced in the following sizes: 10x2; 8x2; 5x3 and 8x3 for digital cross.

Distinguish between the station and the main part of the cross.

That part of the cross to which all ports of the UPATS are connected is called the station side.

The part of the cross to which the wires from the subscriber outlets are suitable is called the main side.

With the help of a crossover cable PKV and a special tool, these parts of the cross are connected.

This allows you to quickly crossover (switch) a pair (landline number, internal number) at the request of subscribers without using the PBX administration program.

Lightning protection for voltage and current can be installed on the cross to protect the equipment that is connected to it (telephones, automatic telephone exchanges, etc.)

Mounting elements:

Mounting clamps

19" constructs

Cross boxes

Cross racks

Service accessories:

Test cords

Mounting tool

Lightning protection elements:

Integrated current and voltage module

Specialized analyzers of telephone lines.

The equipment of the premises of the cross-country telephone exchanges includes test-measuring tables (IMS) designed for the production of operational measurements and testing of subscriber lines, telephone sets, subscriber sets of automatic telephone exchanges and connecting wires.

IMS equipment for electromechanical stations can be divided into five main parts:

Connecting device for connecting the IMS to the tested connecting (subscriber) line

Test part to determine

Serviceability of the subscriber line, telephone set and subscriber set of automatic telephone exchange;

Measuring part for operational measurements of the electrical parameters of the line and TA on direct current;

Service part for receiving applications and conducting a conversation with the subscriber and personnel of the automatic telephone exchange;

Intercom for dialing, receiving and transmitting a conversation, used in conjunction with the test and service part.

Technical capabilities of IIS:

Connecting device.

The connecting device allows you to connect the IMS to the line under test either using automatic data setting devices, by dialing the number of the tested TA, or in a cross using test cords. Automatic connection is possible only to subscriber lines, and with the help of cords - to any connecting lines.

Test part.

The test part of the IMS allows you to:

Call the subscriber who has the tube down with inductive current;

Call the subscriber, who is off-hook, with a phonic signal of increasing volume;

Monitor the progress of connection establishment and conversation on the tested line;

Call the station on the checked line and dial any number;

Negotiate on the checked line both towards the line and the station;

Check the quality of conversational TA circuits by introducing an artificial line with attenuation of 26 dB into the conversational path during a conversation;

Check the correct operation of the SLT dialer connected to the line.

measuring part.

The measuring part allows:

Measure the ohmic resistance of the loop of the subscriber and connecting lines (both two and three-wire);

Measure the insulation resistance between wires A and B of the subscriber line, as well as between any wire and ground within the range of up to 1-10 Ohm;

Check for the presence of a line of extraneous polarity on the wires by measuring the insulation resistance between each wire and the minus of the ATS batteries;

Check the integrity of the capacitor in the subscriber's telephone;

Check the safety fuses of the cross.

In general, IIS allows you to check the telephone line for unauthorized connection in all modes of operation of the telephone. Electronic PBXs of the latest generation have a rich set of service functions, so the detection of illegal connections is greatly simplified. Naturally, only employees of the automatic telephone exchange can perform such work.

It seems interesting to use devices designed specifically for information security to control the line. From the total amount of data obtained with the help of such specialized testers, it is necessary to select those that indicate the facts of connecting various devices to the line, line breaks, etc.

Testing and measuring table IMS.

Tonal telegraphy equipment TT-144.

The telegraphy equipment TT-144 is made according to the FDM principle with frequency modulation and is intended for organizing telegraph channels on the main section. It operates via PM channels of cable, overhead or radio relay communication lines.

Tonal telegraphy equipment TT-144

A discrete electrical signal (DS) differs from an analog one in that its parameters (duration, amplitude, frequency, and phase) can only take values ​​that differ sharply from each other. In this case, the transmission of any symbols is pre-encoded with a certain combination of characters with two or more different states, and this code combination is already transmitted to the line in the form of a DS sequence.

In the simplest case, the DS is transmitted in the form of bipolar or unipolar DC pulses. With more complex transmission options - in accordance with the primary code, it changes

one of the parameters of the harmonic (analogue) oscillation of some reference oscillator, which takes a well-defined discrete-significant position. As you know, the transmission of DS is characterized by its speed FROM, which is understood as the number of binary elements of the primary code of the message transmitted in one second (bps). The rate at which single elements follow when transmitting a codeword is called the modulation rate (or telegraphy rate) AT, Baud. These quantities are interconnected by the following relation

C \u003d B log2 m,

where m- the number of significant positions of the DS (base of the code).

Obviously, for two-position DS, i.e. at m = 2, C = B, and for multi-position signals, the data transfer rate exceeds the telegraphy rate in log 2m once.

So, for example, in conventional telegraphy with speeds up to 300 Baud and data transmission systems with speeds up to 1200 bps operating in the frequency band of a standard PM channel, two-position signals are usually used. If it is necessary to provide data transfer rates from 2400 bps and higher, such multi-position signals are already used, at which the modulation rate does not exceed the limit for the standard telephone channel band - 1800 Baud.

The transmission of DS over communication channels is accompanied by distortions of single pulses, which manifest themselves in their splitting and shifting of the fronts (significant moments of demodulation). The causes of edge distortion are transients in lines and filters, signal level fluctuations, and noise interference. Their permissible value is determined by the nominal corrective capacity of the receiving part of the equipment.

When using unipolar messages for transmission of DS, terminal telegraph equipment is more easily implemented, but the signal in this case is less resistant to the above distortions. The use of bipolar pulses leads to a complication of the transmitting equipment, but on the other hand, the noise immunity of telegraph communication increases and its range along conventional physical circuits increases.

For the correct reproduction of DS code combinations and their automatic conversion into characters, synchronous and in-phase operation of the terminal receiving and transmitting equipment is necessary. Therefore, even in single-channel DS transmission systems, distributors are obligatory elements that phase the operation of the terminal equipment in cycles. In this case, two main methods of phasing (and transmission of DS, respectively) are used: synchronous (continuous) and start-stop (intermittent).

With the start-stop method of transmitting the DS, the distributors start working only at the moment the transmission of the code combination begins, which begins with the starting (currentless or negative) pulse (Fig. 3.26).

Rice. 3.26. Start-stop cycle of transmission of the code combination DS

After passing through the combination (i.e. after the completion of the cycle), a stop (current or positive) pulse is issued and both distributors stop, restoring the in-phase position. It is obvious that the receive cycle cannot coincide exactly with the beginning of the start message, since for some time t1, especially in electromechanical devices, is spent on starting the receiving distributor. It also stops with some delay. t2. Therefore, the reception cycle in the terminal equipment is deliberately made somewhat shorter than the transmission cycle. For example, if when using the MTK-2 code, the transmitting cycle will be

T lane \u003d 6t 0 +t st,

then the receiving cycle should be equal to

T pr . o fri \u003d 6t 0 +0.5t ct +0.5 (t 1 -t 2) .

The specified difference in cycles is provided by the appropriate setting of the drive mechanisms of the terminal start-stop equipment. So, for the LTA-8A apparatus, the engine speed during transmission is set to 400.9 rpm, and at reception - 463.6 rpm.

Random offset of the start pulse can lead to incorrect reception of one or more codewords. Therefore, the noise immunity of the communication channel in this case is low.

With the synchronous transmission method of the DS, at the end of each operation cycle of the transmitting distributor, a special correction pulse is issued to adjust the phase of the receiving distributor, and in the absence of information symbols, a service (stop) combination is issued to the channel that does not cause a character to be printed. Thus, synchronous terminals ensure that patterns are continuously transmitted, whether a message is being transmitted or not.

The divergence of the phases of the distributors in this case is small and the noise immunity of the DS transmission channel is noticeably higher.

The phasing method also determines the method of entering messages into the transmitting distributor: synchronous or asynchronous, as well as the complexity of building telegraph equipment.

Asynchronous message input provides a start-stop method for transmitting a DS. At the same time, the terminal equipment turns out to be much simpler in design and more reliable in operation. Therefore, in telegraphy, start-stop devices have become overwhelmingly widespread.

In the case of synchronous transmission of DS, code combinations should arrive at the input of the equipment only at certain points in time - in time with the operation of the distributor. Therefore, purely synchronous DS transmission systems can only be used for automatic, continuous data transmission and at speeds of more than 600 baud.

Combine the advantages of both systems: high noise immunity of communication with synchronous phasing in a cycle, simplicity of equipment and convenience of asynchronous message input allow start-stop-synchronous DS transmission systems. In these systems, the terminal transmitting and receiving equipment is start-stop, and the transmission of code combinations over the communication channel is carried out in a synchronous manner. The conversion of a start-stop code combination into a synchronous one is carried out automatically using a special start-stop-synchronous device.

As noted above, the simplest discrete signals are direct current pulses, so for many decades telegraph communication with the transmission of such pulses through physical circuits was the only means of transmitting messages over cable lines over long distances.

In most cases, start-stop devices (STA, LTA) with the MTK-2 code and operating speeds up to 200 baud are used as terminal devices. The edge distortion of their transmitting part does not exceed 5%, and the correcting ability is not less than 40%. CTAs work with single-pole sendings of direct current 40-70 mA and voltage up to 120 V (in LTA devices, the voltage is reduced to 20 V). This causes mutual interference in the circuits and significant edge distortion of the pulses themselves. Therefore, as a rule, telegraph equipment includes transitional (matching) devices (PU) for converting single-pole parcels into two-pole ones, and the input circuits of the channel-forming equipment are designed to work with two-pole parcels.

To ensure the given reliability of telegraph communication, the values ​​of edge distortions are normalized as follows:

STA transmitter - up to 5% during setup and up to 8% during operation;

synchronous devices - up to 4%;

switching devices up to 2%;

subscriber section - up to 12%;

main section - up to 30%.

In cases where the norms of edge distortions are not met, intermediate start-stop or synchronous regenerators are used to correct these distortions.

At the same time, with this method of transmission, the spectrum of the DS signal is quite wide and, due to the strong dependence of the characteristic parameters of the circuits on the frequency, there are quite strong distortions in the shape and duration of the DS. This circumstance significantly limits the speed of telegraphy and the range of communication without re-reception of messages. In addition, when telegraphing with direct current, difficulties arise in the construction of multi-channel transmission systems for DC.

Despite these shortcomings, this method of telegraphy is still economically feasible and finds its application in the lower links of secondary telegraph networks - on connecting and subscriber lines.

It should be noted that at a new, high-quality turn of its development in multichannel systems with a VRC, the use of DS transmission by DC pulses through a physical circuit is already becoming expedient on intrazonal telegraph networks.

(to the begining )

3. 5 .2. Frequency division of telegraph channels

The problems that arise during the transmission of DC over physical circuits by direct current pulses, as well as the widespread use (at one time and even still) on the main communication lines of PM channels, determined the predominant development in all the main links of military telegraph communication networks of the so-called voice-frequency equipment. telegraphy. This equipment uses the principles of frequency division of channels and more complex options for transmitting DS, when one of the parameters of the harmonic (analogue) oscillation changes in accordance with the primary code.

At the same time, on trunk and intrazonal communication lines, as a rule, voice-frequency telegraphy equipment (TT) operating over telephone channels (secondary compression equipment) is used, and on short lines where there is no channel-forming equipment, physical circuit compaction equipment in the same tonal range frequencies or beyond. This turns out to be more economical than the formation of special telephone channels with their subsequent compaction with TT equipment.

The TT equipment uses the principle of converting DC pulses into voice-frequency bursts during transmission and inverse conversion - during reception. For this purpose, most often, frequency modulation is used, which ensures ease of implementation of equipment with high channel quality.

The functional diagram of the formation of a multi-channel TT-FM path is shown in Fig. 3.27. The main elements of the device for converting signals to transmit in each channel are a frequency modulator and a band pass filter for transmission. The FM is a switchable tone generator. Its switching is carried out in accordance with telegraphic messages, for example, using a relay or an electronic key.

Rice. 3.27. Block diagram of the TT-FM system.

The device for converting the signals of each channel at the receiving end consists of a bandpass filter, which determines the band of the given channel, an amplifier with an amplitude limiter, and a frequency demodulator. Further, the currents of working parcels from f n and f in arrive at the comparison circuit (for example, into the windings of a polarized relay), where rectangular DC packets are formed to power the receiving part of the CTA. Usually, the frequency response is implemented in the form of a frequency discriminator, since narrow-band filters are much more difficult to implement.

When transmitting a current message to the FM, a frequency is generated

f n = f cf -D f d ,

and with currentless (or with negative)

f in = f cf +D f d ,

where D f d - generator frequency deviation;

f cf th average (carrier) frequency.

The spectrum of the FM signal is determined, as is known, by the speed of telegraphy AT = 2F and the magnitude of the frequency deviation. These quantities are interconnected through the modulation index

m =D f d/F,

where F is the manipulation speed.

In TT-FM systems, the value m lies, usually, in the range of 1.8-2.0, and since for m < 3 полоса частот ЧМ сигнала равна

D f c = 2F(m+1) = 2F + 2D f d.,

then at AT= 50 Baud, the required bandwidth of one telegraph channel will be 140 ¸ 150 Hz with D f d 45-50 Hz. Taking into account the width of the guard bands for reliable filtering, the frequency band for one TT-FM channel can be 180-190 Hz

It should be noted that TT channels, designed for telegraphy at 50 baud, also provide operation at 75 and 100 baud. This is explained by the fact that with an increase in B at a constant frequency deviation, the frequency modulation index decreases proportionally, i.e. the required channel bandwidth is maintained.

Channel carriers f compare i are chosen so that the second harmonics of the operating frequencies f n and f in of one channel would not coincide with the operating frequencies of other channels, but would fall into the filtering zones or coincide with the average frequencies of the channels. These requirements are satisfied by such a ratio between the frequencies

f cf. i[Hz] = 270 + 180i

where i- channel number.

Thus, up to 17 TT-FM channels with a transmission rate of up to 100 baud can be placed in one standard PM channel (Fig. 3.29).

Rice. 3.28. Secondary compaction of the PM channel by TT-FM equipment

The main advantage of TT-FM systems is that in the comparison circuit at the reception, an automatic comparison of the difference in the envelopes of tonal bursts is performed. f n and f in with a zero threshold, independent of the signal-to-noise ratio. In this case, if the interference equally affects both messages, then in the comparison circuit this effect will be compensated, i.e. reception immunity is increased. For the same reason, TT-FM systems little sensitive to change the signal level in the channel.

The disadvantage of this system is the increased sensitivity to frequency changes in the channel. Yes, deviation. f Wed only 5 Hz leads to a distortion of the duration of the parcels by 10%. This implies the corresponding requirements for the frequency stability of the generator equipment and for the characteristics of the PM channel.

(to the begining )

3. 5 .3. Temporary separation of telegraph channels

The operation of equipment for temporary compression (decompression) of telegraph channels is based, as a rule, on the fact that elementary impulses t0 code combinations of various telegraph messages are gated by short clock pulses t 0 <<t0, usually in the middle - less distorted part of them. In this case, the duration of clock pulses t 0 are determined from the fact that during the time allotted to one elementary pulse of the code combination t0 strobing of the elements of the entire set of code combinations in the combined channels should be provided, that is:

To implement the specified principle of forming a group video signal, the input and output of each of the telegraph channels must be equipped with: an accumulator of signs of code combinations of telegraph messages and a distributor-regenerator that provides strobing of these combinations (Fig. 3.29).

Rice. 3.29. Structural diagram of the system of time division of telegraph channels

Group equipment, in this case, must be represented by synchronous distributors for transmission and reception, i.e. - schemes of temporary unification and separation of telegraph messages.

Time diagrams of HW formation with this variant of time division of telegraph channels are presented in Fig. 3.30.

Rice. 3.30. Diagrams of HW formation during time division of telegraph channels

Individual transmission and reception units, consisting of accumulators (for the MTK-2 code for 7.5 parcels) and channel distributors-regenerators, ensure the coordination of the start-stop operation of the TA (asynchronous message input) with the synchronous operation of the group distributor.

Channel distributors alternately supply strobe pulses to elementary pulses of code combinations. Based on these pulses, the form and duration of elementary parcels in the regenerators are restored, from the output of which they are removed by a synchronous group distributor. During one elementary parcel t o the distributor must count the pulses from the regenerators of all n channels, so the speed of their following in the group signal

,

where AT- telegraphy speed in one channel.

The operation of the synchronization system is provided by a highly stable master clock frequency generator, which controls the operation of the transmitting synchronous distributor and the distributor-regenerator. Adjustment of the frequency of the clock pulses of the receiving distributor is carried out by a synchronizing device that extracts the clock frequency from the HS. To ensure the in-phase operation of the receiving distributor, the last telegraph channel is used, in which a special code combination of phase correction (CF) is transmitted. It is allocated in the phasing device (FU) of the receiving distributor and is used to adjust its cyclic phase.

Multichannel telegraphy systems built according to the considered option, with the addition of another stage of group video signal conversion, for example, using FM to voice-frequency range, can use standard PM channels as the transmission channel of the primary network. The separation of such multichannel trunks within the PM channel itself is already carried out by frequency. In this case, it is customary to talk about the frequency-time multiplexing of telegraph channels,

To unify the equipment in all frequency subchannels, it is advisable to use the same FM, and to ensure the diversity of the subchannels in frequency due to an additional conversion stage using, for example, AM and transmission to the OBP channel.

At the receiving end, the inverse frequency conversion is performed in the AM demodulator, the signal is amplified and the HS is formed using a frequency discriminator, the shape and duration of the bursts t o are restored in it using a regenerator, the distribution of these pulses among individual receiving units, and restoration in them by strobe pulses of duration telegraphic parcels and their submission through an electronic telegraph relay to the TA.

Thus, the range of the PM channel is divided into separate sufficiently wide-band frequency channels with FM, which provide the transmission of DC bursts at speeds up to 600 baud. When using FM with a modulation index close to one, the width of the frequency channel will be somewhat larger than 2F GS or B GS. Consequently, with this option of constructing sealing systems in one PM channel, it is possible to ensure simultaneous operation of up to 48 telegraph channels.

For compaction of only physical circuits of small length, multichannel telegraphy systems with RTOs using only one AIM stage can be used.

Unlike FCT, in these systems, the strobing of the telegraph pulse is performed repeatedly. In this case, the strobing (or quantization) frequency is selected based on the permissible value of telegraphic distortions, and reaches tens of kilohertz. In the interval between two adjacent pulses reflecting the state of a given channel, under the condition  0 << t sq the transmission of quantization pulses of the remaining channels is carried out (Fig. 3.31).

Rice. 3.31. Telegraph signal quantization for VRK with AIM

Such constant scanning strobe pulses(at a higher speed), firstly, it allows to determine the significant moments (beginning and end) of information packages with a small error and eliminate the need for an interface device for start-stop and synchronous cycles of the input channels and the transmission distributor. And, secondly, along with the subsequent conversion of the HS into a pseudo-ternary code, which excludes the constant component of the spectrum, it makes it possible to work in the region of higher frequencies, where, as is known, the amplitude and phase distortions of the signal are much less.

(to the begining )

3 . 5 .four. Basic multichannel telegraphy systems

As noted above, multichannel telegraphy systems can be divided into systems designed for secondary multiplexing of standard telephone channels, and systems operating directly over physical circuits of cable lines or radio channels. The first ones are mainly used on trunk and intrazonal communication lines, and the second ones - in the lower links of the telegraph communication network, the compaction of which with two types of equipment is not economically feasible.

The performance characteristics of the main types of TT-FM equipment that are found on the US Armed Forces and the Navy are given in Table 3.6.

Table 3.6.

Tactical and technical characteristics of TT-FM equipment

It should be borne in mind that such equipment as TT-17p, TT-48 and TT-144 refers to general-purpose systems.

So TT-17p, having a number of modifications (1,2 and 3) and allows you to form up to 17 channels with telegraphy speeds of 50 and 75 Baud in a standard PM channel. 180 Hz is assigned to each channel (140 Hz - channel width with a deviation of 50 and 40 Hz - for filtering). The total number of channels is formed from two groups of 6 and one group of 5 TLGk. The main one is a 6-channel (second) group with a band of 1460-2500 Hz, from which the first 6-channel group (300-1420 Hz) and the third 5-channel group with a band of 2540-3400 Hz are formed using group conversion. At the same time, it is possible to transmit each group via a separate telephone channel.

Equipment TT-48 provides 24 CT channels at 50 Baud, 12 channels at 100 Baud or 6 channels at 200 Baud in the frequency band 380-3220 Hz. However, equipment for 48 TT channels is placed on one rack. Therefore, it is possible to connect up to 8 telephone channels and various combinations of telegraph channels. The transition from one speed to another is made by replacing the channel blocks. The characteristics of the TT channels that are provided in this case are given in Table 3.7.

Table 3.7.

Characteristics of the channels of the equipment TT-48, 144

Usually, 2 PM channels are connected in one rack, in each of which TT channels are formed at different telegraphy speeds. The primary group is 12-channel with a band of 300-1820 Hz, one of which is transferred to the frequency spectrum of 1820-3220 Hz using group conversion. Edge distortions in the channels do not exceed 5%.

Equipment TT-144 is a relatively new generation of equipment, made at the level of world standards, with digital signal processing, quartz stabilization of not only the frequency of the transmitter and receiver, but also bandpass filters. It also provides for: restructuring of universal blocks of individual equipment for different telegraphy speeds using active RC filters-converters, automatic adjustment of predominance, automatic control of PM channels by residual attenuation and carrier frequency deviation.

This equipment ensures the operation of up to 144 TT channels due to the simultaneous multiplexing of 6 standard telephone channels, in each of which it is possible to organize the number of channels indicated in the corresponding line of Table 3.6 or 1 data transmission channel at 1200 Bd.

Samples of military field equipment have also been developed on the basis of general-purpose systems. So, in the past, TT equipment from the Topaz series was most widely used in the Armed Forces (including the Navy). P-318

At present, it has been replaced by the P-327 complex, which is designed to form TT channels and low-speed PD channels in networks and on direct communication lines of various control links.

The complex includes the following devices: P-327-12, P-327-3, P-327-2, P-327-PU-6, P-327-PU-1, P-327-TPU.

P-327-12 provides receiving 12 100-baud TT channels in one TP channel (1 TP mode) or 6 TT channels in 2 TP channels (2 TP mode). In the 6-channel mode, it is possible to connect to each set of P-327-12 equipment the intercom P-327-TPU for intercom communication over a narrowed TLF channel of 0.3-1.6 kHz .. P-327-12 is interfaced with P-318-6, P-319 (A, B), TT-144, TT-48, TT-12, TT-17p.

P-327-3 allows you to form three 200-baud CT channels in a standard TF channel. Two sets of P-327-3 equipment can work on one PM channel. It interfaces with the following types of equipment P-319-3, TT-144, TT-48, TT-12 and has 3 operating modes:

mode B - operation on one PM channel, with the formation of 3 TT channels in the band 1.8-3.4 kHz;

mode B (VD) - B - leading - similar to mode B, but it becomes possible to connect another set of P-327-3 or P-327-TPU to the P-327-3 equipment;

mode A (VM) - the equipment forms three TT channels in the frequency band of 0.3-1.8 kHz and makes it possible to connect to the leading P-327-3 (the P-327-3 equipment cannot work independently in this mode).

P-327-2 allows you to create 2 100-baud channels or 1 75-baud channel for working with P-314m, P-317. The TLF channel is saved. P-327-2 can work directly on two-wire circuits, providing the formation of one 100-baud TT channel and one TLF channel.

The channels of the P-327 complex are asynchronous, so transmission can be carried out at any speed from 0 to 100 (200) Baud.

P-327-TPU includes telephone intercoms for receiving 6 service channels over 6 PM channels. Each TPU occupies a band of 0.3-1.6 kHz and can work with P-327-12 equipment installed in 6-channel mode or with P-327-3.

P-327 is connected to HF channels of wired, RR and tropospheric communication lines using a 4-wire circuit with relative levels - 13 dB (-1.5 Np) for transmission and +4.3 dB (+0.5 Np) for reception .

The nominal reception levels of P-327-12 equipment are -15.5 dB (-1.73 Np), and P-327-3 - -12.5 dB (-1.4 Np). Distortion » 5%, with an increase in speed by 1.5 times - up to 10%.

(to the begining )

3.3.

3.7. Structure and typical equipment of multichannel fiber-optic communication systems

3.8. Switching systems